package com.icbc.util;




public final class RSABase64Util {  
	  
    static private final int     BASELENGTH           = 128;  
    static private final int     LOOKUPLENGTH         = 64;  
    static private final int     TWENTYFOURBITGROUP   = 24;  
    static private final int     EIGHTBIT             = 8;  
    static private final int     SIXTEENBIT           = 16;  
    static private final int     FOURBYTE             = 4;  
    static private final int     SIGN                 = -128;  
    static private final char    PAD                  = '=';  
    static private final boolean fDebug               = false;  
    static final private byte[]  base64Alphabet       = new byte[BASELENGTH];  
    static final private char[]  lookUpBase64Alphabet = new char[LOOKUPLENGTH];  
  
    static {  
        for (int i = 0; i < BASELENGTH; ++i) {  
            base64Alphabet[i] = -1;  
        }  
        for (int i = 'Z'; i >= 'A'; i--) {  
            base64Alphabet[i] = (byte) (i - 'A');  
        }  
        for (int i = 'z'; i >= 'a'; i--) {  
            base64Alphabet[i] = (byte) (i - 'a' + 26);  
        }  
  
        for (int i = '9'; i >= '0'; i--) {  
            base64Alphabet[i] = (byte) (i - '0' + 52);  
        }  
  
        base64Alphabet['+'] = 62;  
        base64Alphabet['/'] = 63;  
  
        for (int i = 0; i <= 25; i++) {  
            lookUpBase64Alphabet[i] = (char) ('A' + i);  
        }  
  
        for (int i = 26, j = 0; i <= 51; i++, j++) {  
            lookUpBase64Alphabet[i] = (char) ('a' + j);  
        }  
  
        for (int i = 52, j = 0; i <= 61; i++, j++) {  
            lookUpBase64Alphabet[i] = (char) ('0' + j);  
        }  
        lookUpBase64Alphabet[62] = (char) '+';  
        lookUpBase64Alphabet[63] = (char) '/';  
  
    }  
  
    private static boolean isWhiteSpace(char octect) {  
        return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);  
    }  
  
    private static boolean isPad(char octect) {  
        return (octect == PAD);  
    }  
  
    private static boolean isData(char octect) {  
        return (octect < BASELENGTH && base64Alphabet[octect] != -1);  
    }  
  
    /** 
     * Encodes hex octects into Base64 
     * 
     * @param binaryData Array containing binaryData 
     * @return Encoded Base64 array 
     */  
    public static String encode(byte[] binaryData) {  
  
        if (binaryData == null) {  
            return null;  
        }  
  
        int lengthDataBits = binaryData.length * EIGHTBIT;  
        if (lengthDataBits == 0) {  
            return "";  
        }  
  
        int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;  
        int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;  
        int numberQuartet = fewerThan24bits != 0  ? numberTriplets + 1 : numberTriplets;  
        char encodedData[] = null;  
  
        encodedData = new char[numberQuartet * 4];  
  
        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;  
  
        int encodedIndex = 0;  
        int dataIndex = 0;  
        if (fDebug) {  
            System.out.println("number of triplets = " + numberTriplets);  
        }  
  
        for (int i = 0; i < numberTriplets; i++) {  
            b1 = binaryData[dataIndex++];  
            b2 = binaryData[dataIndex++];  
            b3 = binaryData[dataIndex++];  
  
            if (fDebug) {  
                System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);  
            }  
  
            l = (byte) (b2 & 0x0f);  
            k = (byte) (b1 & 0x03);  
  
            byte val1 = ((b1 & SIGN) == 0)  ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            byte val2 = ((b2 & SIGN) == 0)  ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);  
            byte val3 = ((b3 & SIGN) == 0)  ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);  
  
            if (fDebug) {  
                System.out.println("val2 = " + val2);  
                System.out.println("k4   = " + (k << 4));  
                System.out.println("vak  = " + (val2 | (k << 4)));  
            }  
  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];  
        }  
  
        // form integral number of 6-bit groups  
        if (fewerThan24bits == EIGHTBIT) {  
            b1 = binaryData[dataIndex];  
            k = (byte) (b1 & 0x03);  
            if (fDebug) {  
                System.out.println("b1=" + b1);  
                System.out.println("b1<<2 = " + (b1 >> 2));  
            }  
            byte val1 = ((b1 & SIGN) == 0)  ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];  
            encodedData[encodedIndex++] = PAD;  
            encodedData[encodedIndex++] = PAD;  
        } else if (fewerThan24bits == SIXTEENBIT) {  
            b1 = binaryData[dataIndex];  
            b2 = binaryData[dataIndex + 1];  
            l = (byte) (b2 & 0x0f);  
            k = (byte) (b1 & 0x03);  
  
            byte val1 = ((b1 & SIGN) == 0) ?  (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);  
            byte val2 = ((b2 & SIGN) == 0)  ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);  
  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];  
            encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];  
            encodedData[encodedIndex++] = PAD;  
        }  
  
        return new String(encodedData);  
    }  
  
    /** 
     * Decodes Base64 data into octects 
     * 
     * @param encoded string containing Base64 data 
     * @return Array containind decoded data. 
     */  
    public static byte[] decode(String encoded) {  
  
        if (encoded == null) {  
            return null;  
        }  
  
        char[] base64Data = encoded.toCharArray();  
        // remove white spaces  
        int len = removeWhiteSpace(base64Data);  
  
        if (len % FOURBYTE != 0) {  
            return null;//should be divisible by four  
        }  
  
        int numberQuadruple = (len / FOURBYTE);  
  
        if (numberQuadruple == 0) {  
            return new byte[0];  
        }  
  
        byte decodedData[] = null;  
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;  
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;  
  
        int i = 0;  
        int encodedIndex = 0;  
        int dataIndex = 0;  
        decodedData = new byte[(numberQuadruple) * 3];  
  
        for (; i < numberQuadruple - 1; i++) {  
  
            if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))  
                || !isData((d3 = base64Data[dataIndex++]))  
                || !isData((d4 = base64Data[dataIndex++]))) {  
                return null;  
            }//if found "no data" just return null  
  
            b1 = base64Alphabet[d1];  
            b2 = base64Alphabet[d2];  
            b3 = base64Alphabet[d3];  
            b4 = base64Alphabet[d4];  
  
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);  
        }  
  
        if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {  
            return null;//if found "no data" just return null  
        }  
  
        b1 = base64Alphabet[d1];  
        b2 = base64Alphabet[d2];  
  
        d3 = base64Data[dataIndex++];  
        d4 = base64Data[dataIndex++];  
        if (!isData((d3)) || !isData((d4))) {//Check if they are PAD characters  
            if (isPad(d3) && isPad(d4)) {  
                if ((b2 & 0xf) != 0)//last 4 bits should be zero  
                {  
                    return null;  
                }  
                byte[] tmp = new byte[i * 3 + 1];  
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);  
                tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);  
                return tmp;  
            } else if (!isPad(d3) && isPad(d4)) {  
                b3 = base64Alphabet[d3];  
                if ((b3 & 0x3) != 0)//last 2 bits should be zero  
                {  
                    return null;  
                }  
                byte[] tmp = new byte[i * 3 + 2];  
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);  
                tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
                tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
                return tmp;  
            } else {  
                return null;  
            }  
        } else { //No PAD e.g 3cQl  
            b3 = base64Alphabet[d3];  
            b4 = base64Alphabet[d4];  
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);  
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));  
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);  
  
        }  
  
        return decodedData;  
    }  
  
    /** 
     * remove WhiteSpace from MIME containing encoded Base64 data. 
     * 
     * @param data  the byte array of base64 data (with WS) 
     * @return      the new length 
     */  
    private static int removeWhiteSpace(char[] data) {  
        if (data == null) {  
            return 0;  
        }  
  
        // count characters that's not whitespace  
        int newSize = 0;  
        int len = data.length;  
        for (int i = 0; i < len; i++) {  
            if (!isWhiteSpace(data[i])) {  
                data[newSize++] = data[i];  
            }  
        }  
        return newSize;  
    }  
}  